You have to make sure ALL pages are properly redirected.
And, yes, you'll still lose some of the juice. Depends where you are in the DA slide (if you are 50 vs 20, e.g., it is completely different ball game and consequences and ease of restoring) and how much of an upgrade is the name you are getting. So, if you are moving from tomcruise8922.com to tomcruise.com, by all means, do it, SEO can be taken care of. But if it is tomcruise8922 to tomcruise892 or bradpitt8922, don't do it.